


I Choose You

by Inell



Category: Teen Wolf (TV)
Genre: Allison Lives, Allison and Derek and Stiles work together, Anal Fingering, Anal Sex, Bottom Derek, But they'll make up because they're BFFs, F/M, Friends to Lovers, Future Fic, Getting Together, Kissing, M/M, Multi, Oral Sex, Pack Disagreement, Polyamory, Romance, Scott and Stiles disagree, Slow Build Derek Hale/Stiles Stilinski, Then Allison joins them, Threesome - F/M/M, Vaginal Fingering, Voyeurism
Language: English
Status: Completed
Published: 2016-01-24
Updated: 2016-01-24
Packaged: 2018-05-15 20:59:22
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,397
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5799949
Author URL: https://archiveofourown.org/users/Inell/pseuds/Inell
Summary: <blockquote class="userstuff">
              <p>After a pack disagreement, Stiles is joined by Derek and Allison to deal with a threat. This gives Derek and Stiles the opportunity to finally explore what's been developing between them, but they don't expect Allison's request to join them.</p>
            </blockquote>





	I Choose You

**Author's Note:**

  * For [Bashfyl](https://archiveofourown.org/users/Bashfyl/gifts).



> For Bashfyl's prompt: Prompt: Sterek/Allison poly.. NSFW.. After a big pack argument people have to take sides and Allison chooses Derek and Stiles over Scott and things develop
> 
> I hope you like this, hon! Thanks so much for the prompt!

Scott is an amazing guy, one of the best ever, but he can be so damn short-sighted sometimes that it makes Stiles want to scream. So many of their enemies have been left alive, allowed to get away, and it’s because Scott is too kind to make the tough choices. Hell, last year is proof of how that trusting innocence can bite the pack in the ass, what with the whole Theo bullshit followed by Gerard and Deucalion both coming back to haunt them like bad pennies.

Despite all this, Scott is still refusing to listen to reason. Sure, Stiles feels bad that they’re going to have to kill someone who seems remorseful, _seems_ being the important word, but he knows what she is, deep inside, and it’s not something that can be controlled. Scott is obviously associating it with his wolf, but it isn’t the same. Stiles knows from experience that it’s impossible to control magic and demons that are so powerful. It isn’t anything personal against Lisa, beyond the fact that she’s dangerous, but she isn’t possessed, she isn’t going to suddenly wake up one day and not be a demon with a thirst for blood, and she isn’t going to just go away to live peacefully.

Stiles tries to be the voice of reason, verbalizing the worst parts of this whole supernatural business because Scott shouldn’t be tarnished with making such tough choices, and it normally works alright. This time, though, Scott is being obstinate, and he’s making it into a fight that has the pack tense and anxious. It would be easy to back down and defer to his alpha, but Stiles _knows_ this isn’t the right choice. He’d seen the smirk on Lisa’s face after Scott fell for every word she said, and he knows this is something worth fighting for because he isn’t planning to let Scott die before him, and he doesn’t want to die today.

“Fine. You do what you have to do, Scotty, but I’m not going to just sit by and let her destroy everything and everyone I love.” Stiles gets up and shakes his head. “If I have to do it on my own, I’ll find the proof, and you’ll see I’m right.”

Derek steps away from the wall that he’s been leaning against. “Not on your own. I’m sorry, Scott, but Stiles is right. You don’t realize what we’re dealing with. She isn’t a victim in this,” Derek says quietly. 

Scott gives him a betrayed look before he tenses in that stubborn ‘people will have to die before I admit I was wrong’ way. “It’s your choice.”

“I know. I choose Stiles.” Derek nods at Scott respectful, but it’s obvious he isn’t changing his mind.

Stiles is shocked that Derek actually chose his side, but he’s not ungrateful. It wouldn’t have been the first time he’d gone solo against Scott and the pack, who always defer to their alpha because they don’t want to take the risk of losing their place in the pack. It’s nice to have someone on his side for once, though. He grabs his laptop and heads out the door, listening to the footsteps of Derek following him.

They go down three flights of stairs and step onto the street before he stops walking and takes a minute to think about what’s just happened. “You really think I’m right?” He looks at Derek steadily, needing to know he’d spoken up because he believed in Stiles and not because of the whatever it is that’s been building between them possibly since they first met.

“No,” Derek says, running his fingers through his hair and frowning. “I _know_ you’re right.”

“Oh.” Stiles smiles slightly as he ducks his head. “Well, Scott would, too, if he could think with his brain instead of his heart occasionally.”

“If he did that, he wouldn’t be Scott.” Derek stuffs his hands in the pockets of his leather jacket and shrugs. “He’s a true alpha for a reason. Besides, that’s what he has us for, to do the things that must be done.”

Before Stiles can reply, the door opens, and Allison storms out. Her face is flushed, her ponytail snapping as she walks, and her eyes are blazing with anger. Stiles is reminded of the stories he’s read about warrior women and can’t help but take a moment to admire the beauty of it. “Scott is insufferable,” she snarls. “He needs to grow a pair and just admit he does this so he can keep his conscious clean.”

“Tell us how you really feel, Aly.” Stiles just grins when she glares at him.

“I’ve finally had enough. Any idiot, hell, even _Liam_ , knows this is a bad decision, and I refuse to sit idly by while you go get your hands dirty, again.” She looks between him and Derek then back again. “I choose you. If you’ll let me help.”

“Seriously?” Stiles clears his throat. “I mean, of course you did, you’re smart. If Lydia were here instead of taking MIT by storm, she’d be out here, too.”

Derek has moved closer to Stiles and is just staring at Allison like he doesn’t trust her. “Why?”

Allison rolls her eyes. “It’s not because I’m suddenly hot for Stiles and have wicked plans for his naked body, so stop the guard dog protective thing.” She suddenly dimples. “Not that you haven’t been looking really good lately, Stiles. College suits you. You know, Derek, I might have to reserve the right to change my answer. I _have_ always wondered what those hands would feel like on my bare skin. Such long fingers.”

“Aly, stop teasing Derek. Derek, stop growling.” Stiles lightly slugs Allison’s arm. “No provoking the werewolf. It’s dangerous.”

“I love living dangerously,” she points out. “It’s not my fault he’s got me thinking impure thoughts about you now.”

“We can deal with impure thoughts after we take care of the threat,” he promises, winking at Derek, who just glowers at them both. Teasing is well and good, but he isn’t going to let Allison interfere with this thing he’s got developing with Derek because it’s more important than some harmless flirting. He focuses them on the task at hand. They start walking away from Scott and Kira’s apartment building, talking in low voices about what they can do to get the information they need to take care of Lisa.

****************

“Why did you buy Funyons?” Derek shifts in the front seat and shoots a glare at Allison, who happily tosses another chip into her mouth. “They stink up the Jeep.”

“Because they’re good.” Stiles pokes Derek’s arm. “Stop trying to pick a fight. We’ve managed an hour without any bickering, so let’s not ruin that record.”

This is the fourth time they’ve met up since the disastrous pack meeting at Scott’s last week. Surprisingly, they work well as a team. Allison is focused and driven and so fucking brave, and Derek is intense and serious and so fucking smart. Stiles isn’t really sure what he adds to the team, other than cunning and sneakiness and the questionable morality that they need to get things done. 

Well, he’s also developing some killer mediation skills. Allison and Derek are always bickering, almost like siblings but with a decidedly non-familial vibe that’s pretty damn hot. The fact that they are usually competing for his attention might have something to do with that hotness factor, of course. There are smiles and touching from Allison that are obviously flirting, usually done when Derek’s there to glare, but there have also been more subtle things she does when it’s just the two of them that make him wonder sometimes if it’s not an act at all.

Still, Stiles isn’t sure if Allison is actually serious or if she’s just enjoying adding another level to her antagonistic relationship with Derek, so he figures there’s no real harm in it. He and Derek are growing closer, the thing between them becoming more tangible and no longer something they can just ignore, and they’ve almost a few different times, getting so close last night that Stiles is annoyed with his dad for coming home and ruining the moment. Allison’s antics seem to actually be making things progress a little quicker between them, in fact. And, sure, when he’s alone at night and jerking off, he’s allowed the odd fantasy or two to develop involving all three of them, but it’s just a fantasy. What he might have with Derek is worth a hell of a lot more than some potentially kinky sex.

The smell of onions gets strong when Allison pokes her arm through the seats and holds the bag between them. “They might not smell good, but they’re delicious. Try some.”

Derek frowns at her before his beautiful eyes cut over to Stiles. He rolls his eyes before he takes a handful. The sound of crunching is heard from all three of them before Derek reluctantly nods. “They’re not bad.”

“You’ve got crumbs,” Stiles says, reaching over to brush his thumb over Derek’s lip, dragging his knuckles across a stubble covered cheek. “Got ‘em.”

“The sexual tension is giving me a headache,” Allison mutters, leaning back and crunching more chips. “Why don’t you just kiss? Don’t mind me. I like to watch.”

“Shut up, Aly.” Stiles drops his hand and looks away, focusing his attention on their target and peering through the windshield. He frowns at the building they’re watching, wondering if Lisa knows they’re out there. He turns towards Derek. “Do you think---“

He doesn’t get to finish his question because Derek’s mouth is suddenly on his. It’s a gentle kiss, not at all like what he expects, almost hesitant like Derek is crazy enough to think Stiles is going to push him away. Stiles reaches over to grip Derek’s neck, moving his lips against Derek’s, shifting in his seat when he feels a tongue flicking out against his lips and teeth. He opens his mouth, teasing Derek’s tongue with his before sweeping it into Derek’s mouth and deepening the kiss. Thank God they’d both eaten Funyons so there wasn’t any chance of Derek being grossed out at the way he tastes. Derek’s hand is on his face, another gripping his hair, and he wishes he could climb into his lap because he’d really like to do that sometime soon.

“Ahem.”

Stiles ignores the sound of a throat clearing and continues to wonder how feasible it is to just climb Derek right here. Derek’s fingers tighten their grip on his hair, tugging slightly, and Stiles moans into the kiss because, yeah, he’s got a bit of a hair kink. Sue him.

“While I’m really enjoying the show, the reason we’re doing this stakeout just left the building and is walking away.”

“Fuck.” Stiles hates to let Derek go, but he has to remember why they’re here. He shoots Allison a dirty look when she lets out a wolf whistle, but she just dimples at him, completely shameless at having sat right there watching them kiss. His dick twitches a little, but he counts until he calms down. 

“We’ll get to that later,” Allison promises, slapping them both on the shoulders. Derek just glares at her, and that makes her laugh. “Let’s go, Stiles, or she’s gonna get away.”

He starts the engine and pulls out, driving along as they follow her to a tea shop and then a yarn store. He parks in the lot of a supermarket because it takes so long at the yarn store. “Do you think knitting needles could kill someone?”

“Yes,” Derek and Allison both answer at the same time. Derek makes a face. “You could puncture skin with enough force, and they’d go through an eyeball or eardrum easily.”

“Also, the smaller ones would be amazingly effective to stab beneath fingernails or toenails.” Allison gets a thoughtful look on her face that reminds Stiles of Warrior Woman instead of giggling matchmaker. 

“That’s a happy thought,” he says, shuddering slightly as he looks back at the yarn store. Derek opens a packet of Reese’s Cups and hands him one, which he takes gratefully. He chews on the yummy combination of chocolate and peanut butter while waiting for the demon bitch to finish buying knitting supplies.

****************

A knock on the door makes Stiles groan. He stops kissing Derek and glares at the offending door, debating whether or not he can just ignore it so he can keep making out with his _boyfriend_. It’s probably a salesperson or something. None of the pack is speaking to him yet, and anyone else is likely to text him or call instead of just showing up uninvited. With that in mind, he grins down at Derek and goes back to kissing his neck, grinding against him as Derek grips his ass tightly. It’s been two weeks since their first kiss in the front seat of Roscoe, and they’ve been steadily growing closer every day. Last night, they’d finally caught Lisa in the act, managing to save her intended victim while Allison and Derek tag teamed her like something out of an action movie.

Now that the big bad is gone, they can actually let their relationship progress, which Stiles hopes means making out without the pesky clothes getting in the way. His dad is on an overnight shift, which means they have the perfect opportunity to turn fumbling hand jobs and grinding against each other into naked fumbling hand jobs and grinding against each other. Maybe even blow jobs. At that thought, he presses down a little more, rewarded by Derek’s soft gasp. Oh yeah. Definitely blow jobs.

The knocking starts again.

“Damn it.” Stiles presses his forehead against Derek’s shoulder. “Can you sniff who it is?”

“I’m not your personal sniffer,” Derek grumbles even as he tilts his head and inhales. His eyes flash blue and he frowns as he sits up. “It’s Allison. She smells anxious and nervous.”

“Oh!” Stiles scrambles off the sofa and heads to the door. He opens it and smiles sheepishly. “Sorry. I thought it was a salesperson or something.”

“Did I interrupt something?” Allison asks as she enters the house, taking a look at Derek sitting on the sofa with disheveled hair and swollen lips. “That would be a yes.”

“Nah, it’s fine. Everything okay?” Stiles walks past her and sits down beside Derek. “Seriously, it’s okay, Aly. We can finish later.”

Allison nods and finally sits down in the chair by the sofa. “Things are good. I mean, we killed the demon before it could kill that guy, and we were proven correct, so Scott’s going to have to come groveling eventually.”

“It’ll take a while. It’s been almost a month, and I haven’t even received any COD invites.” Stiles shrugs. “Something else evil will come along and, if it takes too long, I’ll just go over and make him get his head out of his ass.”

“Good luck,” Derek says dryly. “It won’t be that long, though. He’s been by a few times, but he never comes to the door.”

“Really?” Stiles grins. “It’s cool how you know that.”

“I see you two are still in the honeymoon stage.” Allison laughs. “Feel free to continue what you were doing before I got here. I’ll stay quiet. Promise.”

“Put the dimples away, Aly. We aren’t giving you a live porn show,” Stiles mutters, leaning against Derek’s chest and stroking his thigh. “If everything’s okay, why’d you come by?”

“What? I can’t stop over and visit the only two people other than my father who are speaking to me?” Aly puts her hand on her chest. “That hurts, Stiles.”

“Awww. You missed us.” Stiles grins. “Alright, the dimples can come back.”

“That’s not the only reason you’re here, is it, Argent?” Derek snorts and rubs his jaw against Stiles’ cheek, the stubble scraping in just the perfect way to leave a mark. 

“You called her Allison a minute ago. Don’t regress, dude. It’s not a good thing.” Stiles tightens his grip on Derek’s thigh when he feels lips against his neck.

“He’s right.” Allison leans forward, putting her elbows on her knees and cradling her chin in her palms. “I’m lonely, but it’s a different kind of loneliness.”

“She’s aroused,” Derek whispers against Stiles’ ear. “She wants to watch us, wants to watch you fall apart, wants to be part of it.”

“Aly, do you want to be with us?” Stiles asks, needing to hear the words to believe them. She ducks her head but nods. “I thought you were just teasing.”

“It might have started off that way, but we’ve spent almost every day together for weeks.” She looks up at him and sighs. “I didn’t mean for it to happen, Stiles. I know you two are like the whole fairy tale thing, but I still want what I want, and I figured I should be honest about it. We always have too much lying and covering up stuff, and I don’t want to do that.”

“Do you want her?” Derek has raised his head and he’s staring intently at Stiles.

“Not enough to risk us,” Stiles says firmly. He leans in to brush a kiss against Derek’s mouth. “Do you?”

Derek smiles wryly. “I wouldn’t be as opposed to it as I would have a few weeks ago.”

“Thanks for that,” Allison mutters, her eyes flicking back and forth between them.

“I can always change my mind,” Derek deadpans, his gaze not leaving Stiles’ face.

“Why don’t we try it and see how it goes?” Stiles suggests before they can start bickering.

“I’ll just sit here and watch, if that’s okay? I, uh, have a bit of a kink.” Allison grins when Stiles looks at her. “I’ll join in later, if it feels right.”

“Why don’t we move this up to my bedroom? I’d feel more comfortable there.” Stiles gets up and doesn’t give them time to answer as he heads upstairs. He hastily straightens up his room when he gets there, shoving a pile of clothes that had been in his desk chair into the closet so Allison has somewhere to sit. Derek shows up first, stripping off his shirt and tossing it on the floor before he sits on Stiles’ bed. Stiles walks over to join him, leaning down to kiss him as he hears footsteps enter the room right before his door closes.

“Take his shirt off,” Derek murmurs, pulling away from the kiss to glance at Allison.

Allison steps closer, her fingers soft against Stiles’ bare skin as she pushes his t-shirt up and over his head. “I want to kiss you,” she says, staring at his mouth. He looks at Derek, who nods slightly. With permission, he kisses Allison, licking into her mouth, stroking her tongue, pulling her against him as she drags her fingernails down his bare back. She pulls away finally, breathless and flushed with shining eyes and a crooked smile. “Wow.”

Stiles laughs before he turns to Derek, straddling his lap and kissing him thoroughly. Derek pulls him down, lying on the bed as Allison moves the chair to get a better view. He hears fabric rustling then the sound of something hitting the floor. When he pulls back from the kiss, he sees that Allison has taken off her shirt. Her tits are nice, round and plump, and he can see her nipples pressing against the fabric of her bra. He winks at her before he starts licking Derek’s chest. He nuzzles the hair there, flicking his tongue out to lick a nipple as he begins to slowly roll his hips.

Derek grips his waist and rolls them over, shifting on the bed so they’re not in danger of rolling off, and then he’s pulling Stiles’ jeans down. Stiles lifts his hips to help, glancing at Allison to see her staring with aroused pleasure as they strip. When Derek pushes his underwear down and stands there naked, Stiles feels his breath catch, like some silly girl in an Austin novel. Only with nudity and less corsets. “You’re gorgeous,” he murmurs, gaze moving down Derek’s body, lingering on the thick cock hanging between his legs. He’s half-hard already, and Stiles licks his lips thinking about having that in his mouth.

“Yeah, he is,” Allison breathes out, hand squeezing her breast as she looks from Derek back to Stiles. “And so are you.”

“She’s right,” Derek murmurs, tugging Stiles’ underwear off and tossing them at Allison. His lips curve into a mischievous smile that makes Stiles’ heart flutter then he’s back on the bed, crawling up his body. “I want you to fuck me. Think you can handle that?”

“Fuck yes,” Stiles moans, pushing up to try to get contact against Derek’s warm skin. “I want to taste you first, though. Been thinking about getting your dick in my mouth for years.”

Derek licks the head of Stiles’ dick but it’s just a teasing swipe of his tongue. He straddles Stiles’ chest and arches a brow. “Can you reach it like this?”

“Just watch me. Dude, I’m totally flexible.” Stiles leans up to lick at the pre-come on the head of Derek’s dick. He tastes so good. The position isn’t the best, but he can make it work. He reaches up to stroke Derek’s dick as he sucks the head, slowly getting more into his mouth as he licks the underside and sucks. Derek makes a broken noise that sounds awesome. Allison seems to agree because she whimpers soon after. There’s the sound of rustling fabric again, then the squeak of the chair. His dick hardens a little more at the realization Allison has just taken off her jeans.

“Your mouth feels so good.” Derek is rolling his hips, fucking Stiles’ mouth and hand, reaching back to stroke his dick. “Aly, you wanna help us out here?”

“Me?” Allison is obviously as surprised by the invitation as Stiles, but he hears her quickly crossing the room. “What do you want me to do, Derek?”

“Get him wet for me.” Derek strokes Stiles’ hair, brushes his thumb over Stiles’ cheek. Allison’s mouth is warm as she licks his dick, her hair against his thighs and belly as she begins to suck. “You like that, Stiles? Like having Aly suck your cock?”

He hums his agreement around the dick in his mouth, scratching Derek’s thigh as he thrusts his hips up into Allison’s mouth. She chokes and coughs but is soon back taking him even deeper into her mouth. If she keeps that up, he’s going to come before he can fuck Derek. He squeezes Derek’s leg, trying to convey this to him, and he seems to understand because he’s soon pulling his dick out of Stiles’ mouth. Saliva covers his mouth and chin, and he wipes his face with the back of his hand as he sits up, needing to see Allison with his dick in her mouth.

She raises her eyes to look at him, sucking even harder as she curls her fingers around his balls and kneads them. He pushes her away, shaking his head. “If you keep that up, I’m going to come,” he says, looking at Derek. “There’s only one place I plan to come right now. Get on your knees, Derek. We’re gonna get you ready now.”

And they do. He and Allison have great teamwork as they use their tongues and fingers to stretch Derek’s ass, listening to his broken gasps as he pushes back to fuck their hands. Stiles kisses Allison as they finger Derek, letting her taste Derek on his tongue. He moves his free hand between her legs, stroking her wet cunt, using his fingers to get her even wetter and make her gasp. When Derek’s ready, Stiles urges him onto his back, needing to see his face right now. It’s their first time, after all, even if Allison’s with them.

Derek’s eyes close, his head falls back baring his throat, and he lets out a low moan when Stiles presses inside him. He’s so fucking tight that Stiles has to go real slow, thrusting in and out gradually, letting him get accustomed to his girth. Allison is behind him, her tits rubbing against his back, her wet cunt brushing against the swell of his ass. “Fuck, he’s beautiful like this,” she whispers, reaching around Stiles to stroke Derek’s chest, fingers tangled in chest hair. Derek whines when Stiles is fully seated, his cheeks flushed, his breath coming in ragged inhales and quick exhales. “Fuck him, Stiles. He needs it so bad.”

Stiles doesn’t need any urging to do that. Allison moves so that she’s lying next to Derek, whispering who knows what in his ear that has him making those lovely noises, her fingers wrapped around his hard dick as Stile fucks him with deep thrusts. Derek clenches his ass around Stiles’ dick, making it even more difficult not to come, and he’s bucking his hips up to fuck himself between Allison’s hand and Stiles’ dick. When he comes, he gasps, spilling seed onto Allison’s fingers and his own belly. Stiles can’t last long after that. His hips start snapping forward as he feels his own orgasm approaching. In a half dozen strokes, he’s suddenly tensing then coming with a grunt.

Allison is licking Derek’s come off her fingers when he comes to himself. Her other hand is between her legs, three fingers moving in and out so quickly he can hear the squelching of her pre-come. It’s hot, and he takes a moment to watch before he eases out of Derek and falls between her legs, licking at her hand and her cunt before sucking on her clit. He uses his fingers, the ones she’d teasingly mentioned fantasizing about, and he makes her come with a cry of his name as Derek sucks her nipples and whispers his own dirty words in her ear.

After they’ve all managed to catch their breaths, he crawls between them and makes them cuddle him. “Later, you’re both telling me what you were whispering because it had to be dirty and it had to be hot,” he informs them, giving them each a lazy kiss before he got comfortable. “But, first, we’re taking a nap so we can rest up for round two.”

**Author's Note:**

> Come find me on [Tumblr](http://inell.tumblr.com) to say hi, leave prompts, or hang out!


End file.
